Protective paper and method of making same



Patented Sept. 7, 1943 PROTECTIVE PAPER AND METHOD MAKING SAME Burgess W. Smith, Rochester, N. Y.,assignor to The Todd Company, Inc., corporation of New York Rochester, N. Y., a

-No Drawing. Application March 25, 1941, Serial No. 385,153

' 7 Claims.

This invention relates to a class of protective paper particularly adapted for checks, drafts, bonds, or other commercial instruments, having as its chief object the provision of advantageous paper of this character of a comparatively simple nature, economical to produce, and applicable to a wide range of conditions and requirements. More specifically stated, this invention relates to that class of protective paper in which the application of chemical eradicators is indicated by the production of a stain in the form of a warning character, word, or symbol. It is an object of the present invention to provide a paper of this characteristic in which the development of the stain producing the warning words or indicia will penetrate well into the body of the paper so that it is not removable by abrasion.

Many prior types of paper have depended upon the bleaching out of a fugitive over-tint with eradicators to indicate the application of the chemical thereto. As such protective tints may be readily restored, the more modern types of protective or safety paper have additional compounds incorporated therein to produce a fiat stain that inhibits successful retinting until the stain is removed. Flat stains of this nature are not ample protection as they could be explained to those who are not aware of their significance as a result of splashing or spilling some dark colored substance thereon. To give such developed stain significance the active material adapted to change color with eradicators has been printed or otherwise applied so as to form latent warning words or indicia.

It is obvious that in the use of latent Warning characters to indicate the application of ink eradicators, they should be provided in a way to resist removal from the paper to the greatest possible degree, and especially resistant to erasure by abrasion of the paper surface. This may be accomplished by having the stain when developed penetrate as deeply as possible into the body of the paper. However, it has been found difficult to have the latent printed warning word or symbol penetrate into the body of the paper as it is impractical to print the same and have it penetrate through the paper. This is largely due to the tendency of an ink'that will penetrate to spread laterally and thereby render the warning indicia indistinct and illegible.

In my Letters Patent Nos. 1;454,837, 1,675,769, 1,689,302, 1,817,171, and 2,032,816, I describe and claim methods of making safetypaper by printing or otherwise applying the initially illegible warning characters on the paper with a substantially colorless stain producing material.

As set forth in an application filed on March 25, 1941, bearing Serial No. 385,152, I have discovered an improved safety paper and method of making same by distributing the stain forming material through the body of the paper and then printing warning indicia thereon with a waterresisting or repelling ink. When ink eradicator is applied to paper so prepared the resisting or repelling ink retards development of the active material selectively so that when the paper is I developed the warning indicia by being lighter than the background are made legible. It should be understood that the distribution of the stain forming material-in the paper itself does not form the warning indicia when developed. The warning indicia areproduced by the selective masking of the action of the eradicator by the resisting or repelling ink. I

My present invention provides a further simple and inexpensive method of producing a protective or safety paper having additional advantages over that presented by the safety paper described in my above nfentioned co-pending application. This invention is for the purpose of accomplishing somewhat similar results but with a different and more flexible method of manufacture. It further provides for the distribution of the stain producing material regardless of the ink used for printing. By means of my present invention I am able to have the warning word developed upon application of eradicator to the paper, sharp and distinct and Well into the body of the paper, and the resultant stain of the paper penetrating through to the other side. i

In preparing paper in accordance with the present invention, I first print or otherwise apply the desired warning indicia on plain paper with a water-resisting or water-repelling ink. After the paper has been so'printed it is immersed in a solution or suspension of active material. The penetration of the solution or suspension of active material is retarded where the protective ink is printed on predetermined areas of the surface of the paper so that the distribution follows in general what is printed upon the paper. It is not essential that the water-resisting or repelling properties of the protective ink remainafter drying. There is some advantage, for certain applications and the use of certain materials, to have it completely evaporate.

The latent warning indicia may be printed or.

similarly applied by the usual well known methods. The resisting or repelling ink may be composed of a simple substance such as a lithographic varnish, with or without addition, such as a flattening agent, or the ink may be volatile. For example, kerosene oil applied with a rubber roller on which the warning indicia are engraved or otherwise formed is very effectual due to its water-repelling action. In due time the kerosene oil evaporates and leaves the surface of the paper without an appreciable trace thereof.

A paper prepared inaccordance with the presvarnish is used it also serves to additionally retard the action of the eradicator and greatly enhances the legibility of the developed word.

It is obvious that in the manufacture of paper by the present method any printing process that will apply a sufiiciently resisting colorless varnish may be used. Immediately after printing, the

paper may be immersed in a solution or suspension of the active material, or if desired good results may be attained by drying the printed indicia and subsequently, at, a convenient time, applying the active material. Furthermore, complete invisibility of the warning indicia is not necessary where the paper is to be provided with additional protection consisting of a plain or intricate design applied as an over-tint, as such tints tend to obscure a faintly visible printing.

The bath or coating used for treating the paper after the printing thereon of the warning indicia is flexible as its composition depends entirely upon the effect desired. There are many materials described in the literature for this purpose and it seems hardly necessary to cite more than two, both of which are very effectual in this instance. The aminobenzothiazole series, particularly those that form highly colored salts such as the product on the market known as Chlorostain, and the hydrochloride of diphenylguanidine are both suitable stain materials. These products are of extraordinary stability and adaptability to this process.

A particularly advantageous feature of my invention is that the background developing inhibits the removal of writing by tracing the word witha brush or pen with eradicator. Such manipulation will not be effectual in changing the meaning of the original writing. The stain will be developed in substantially the same form as the original writing, as the entire area contains sufficient reactive material to form the writing sufficiently to be legible.

While the foregoing discloses satisfactory ways of practicing the present invention to produce a protective paper which will admirably fulfill the purpose intended, it is not the desire to be limited in any way of practicing the invention or to any form of the resulting material, as both are capable of numerous changes and modifications, all coming within the scope of the claims which follow.

I claim as my invention:

1. A protective paper having inherently warning indicia printed in a relatively small size and closely repeated arrangement thereon in a substantially colorless protective masking varnish adapted to retard absorption at the areas of the paper surface so protected, and having a coating of stain producing material capable of reacting with chemical eradicating means and being adapted to penetrate into the unprotected portions of the paper, said material being initially substantially colorless but being adapted to react with and to produce a conspicuous color when acted upon by chemical eradicating means applied to the paper for making erasure.

2. A protective paper having matter applied in repeated arrangement thereon in a substantially colorless varnish medium adapted to protect predetermined areas of the paper, and having a coating of stain producing material capable of reacting with chemical eradicating means and being adapted to penetrate into the unprotected portions of the paper, said material being initially substantially colorless but being adapted to react with and to produce a conspicuous color when acted upon by chemical eradicating means applied to the paper for making erasure.

' 3. A protective paper having inherent warning indicia printed in repeated arrangement thereon in a substantially colorless protective varnish medium, and having a coating of stain producing material capable of reacting with chemical eradicating means and being adapted to penetrate into the unprinted portions of the paper, said material being initially substantially colorless but being adapted to react with and to produce a conspicuous color when acted upon by chemical eradicating means applied to the paper for making erasure, and having marked thereon also an additional pattern adapted to be removed by abrasive treatment of the paper to aiford warning of attempted erasure of matter written on the paper.

4. An article of manufacture, a check made of protective paper having warning indicia printed thereon in relatively small size and closely repeated and staggered arrangement with a substantially colorless permanent masking varnish, and having a uniform treatment of active material capable of reacting with chemical eradicating means and being adapted to penetrate into the unprinted portions of the paper, said active material being initially substantially colorless but being adapted to conspicuously alter in color by the reaction with chemical eradicating means applied to the paper for making erasure and thereby rendering said indicia conspicuously visible by reason of the color change of the unprinted background portions of the paper.

5. The method of making protective paper which consists in printing thereon with a substantially colorless masking varnish warning words or indicia, and then applying a solution of a material capable of reacting with ink eradicators to produce a conspicuous color. stain, and drying said paper.

6. The method of preparing protective paper ,that is capable of developing warning indicia upon the application of chemical eradicators, which comprises first in printing wa ning indicia on the paper with a substantially colorless protective varnish, and then uniformly applying a substantially colorless material of a character adapted to have its color conspicuously altered by the reaction of chemical eradicators.

7. The method of preparing protective paper which comprises first printing Warning indicia 'on the paper with a substantially colorless protective masking varnish, and then uniformly applying a substantially colorless material of a character adapted to have its color conspicuously altered by the action with chemical eradicators, and then overprinting said paper in a relative erasible ink, a tint or pattern,

BURGESS W. SMITH. 

